05000325/LER-2016-004
| Brunswick Steam Electric Plant (Bsep) Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3252016004R00 - NRC Website | |
comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
Brunswick Steam Electric Plant (BSEP) YEAR SEQUENTIAL NUMBER REV NO.
Unit 1 05000-325 2016 - 004 - 000 Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
Background
Initial Conditions On July 21, 2016, Unit 1 and Unit 2 were both in Mode 1 (i.e., Run mode) at 100 percent of rated thermal power. Except as described below, no out-of-service equipment contributed to, or affected the course of, this event.
Reportability Criteria This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) because Units 1 and 2 were operated in a condition prohibited by the Technical Specifications (TS). Specifically, the Unit 2 "B" Nuclear Service Water (NSW) [BI] pump was inoperable because some of its control cables were vulnerable to a postulated tornado missile. Both units' TS require at least three of four site NSW pumps to be operable when the units are at power. Therefore, inoperability of the Unit 2 "B" NSW pump alone did not require entry into a TS condition.
- Inoperability of a second NSW pump constitutes a loss of one required pump. In both units' TS, Limiting Condition for Operation (LCO) 3.7.2, Condition B, says that with one NSW subsystem inoperable for reasons other than Condition A (i.e., one required NSW pump inoperable due to header inoperable on the opposite unit), the system must be restored within seven days or be in Mode 3 (i.e., Hot Shutdown) within the following 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
When the affected Unit 2 NSW pump was considered inoperable due to tornado missile vulnerability, and an additional site NSW pump became unavailable, then the plant entered Condition B as described above. In the past three years, two instances were identified in which the plant entered this condition, and the time to restore compliance with the LCO exceeded seven days, twelve hours. Therefore, the plant was operated in a condition prohibited by the TS. The two instances occurred as shown below.
Pumps Out of Service Beginning of Condition End of Condition Duration 2B and 1B NSW Jul 8, 2013 at 2:05 EDT Jul 19, 2013 at 1:00 EDT 10.95 days 2B and 1B NSW Aug 26, 2013 at 1:39 EDT Sep 5, 2013 at 5:43 EDT 10.17 days This event did not result in the safety function of NSW being lost because sufficient NSW capacity remained available in the two pumps that remained unaffected on each occasion. Additional cooling capacity available via Conventional Service Water (CSW) [KG] pumps which can be aligned to supply the NSW header.
comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
Brunswick Steam Electric Plant (BSEP) 004 05000-325 2016 - 000
Event Description
On July 21, 2016, Engineering personnel determined that a conduit associated with Unit 2 NSW pump "B" was vulnerable to a tornado missile. The affected pump was declared to be inoperable. Immediate compensatory actions were implemented in order to satisfy the conditions for enforcement discretion as set forth in Enforcement Guidance Memorandum (EGM) 15-002 and Interim Staff Guidance (ISG) DSS-ISG-2016-01, Appendix A. With these actions in place, NSW pump 2B was then declared to be operable but nonconforming.
Event Causes The vulnerability of the control cables for Unit 2 NSW pump "B" to a tornado missile has existed since original plant construction.
Safety Assessment The purpose of the NSW system is to provide cooling water for safety-related plant equipment such as the Emergency Diesel Generators [EK] and Emergency Core Cooling System pump seals and room coolers, and to serve as the Ultimate Heat Sink for the plant. Two occasions in the past three years were identified in which a required NSW pump was inoperable for greater than seven days, twelve hours. During this time, at least one NSW pump remained operable on each unit, ensuring the safety function was met.
CSW pumps were also available and can be used to supply NSW headers on both units.
Per EGM 15-002, the NRC has analyzed risk generically for tornado-generated missiles. The analysis supports the characterization of the risk as of low significance.
Based on this analysis, this event had no adverse impact on the health and safety of the public.
Corrective Actions
In accordance with EGM 15-002 and Regulatory Issue Summary (RIS) 2015-06, the following compensatory measures have been implemented:
- Procedures were verified to be in place that address high winds, tornadoes, and the potential loss of equipment found to be vulnerable to, a tornado missile.
- Procedures were verified to be in place, and training either received or planned, for responding in the event that a tornado watch or warning is issued.
- Procedures and equipment were verified to be in place supporting Diverse and Flexible Coping Strategies (FLEX).
- The level of awareness by shift personnel was heightened by referencing the 2B NSW pump in shift turnover notes and the discussion of non-conforming conditions.
More comprehensive measures will be implemented within the 60-day period specified by EGM 15-002.
These actions will be in place by September 19, 2016.
comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
Brunswick Steam Electric Plant (BSEP) 05000-325
3. LER NUMBER
2016 , 004 - 000 The above compensatory actions will remain in place until the tornado missile vulnerability is permanently eliminated. This will be completed within the time period specified by EGM 15-002 for plants designated as being in a region of higher tornado missile risk.
Previous Similar Events
No previous events have occurred in which a structure, system, or component has been found to be vulnerable to a tornado missile.
Commitments This report contains no new regulatory commitments.